1. Field of the Invention
The present invention relates to playback control techniques for playing back digitalized movie productions and relates to improvement in order to apply these techniques to playback apparatuses for optical discs and playback authorization servers.
2. Description of the Related Art
Distribution of movie productions, via optical discs, is one of the main sources of income of the movie businesses including, for example, the movie business of Hollywood. In order to be successful in the movie businesses, it is necessary to solve sensitive problems in each distribution area, such as problems related to the relationships with the distribution company in the distribution area, the release period of the movie in the distribution area, and the ethical, historical, or religious viewpoints in the distribution area. In order to solve these problems altogether, the region code system is used in DVDs and playback apparatuses. A region code indicates a region in which it is possible to play back the DVD. When a DVD is loaded, a playback apparatus reads the region code recorded on the DVD, and judges whether the region code matches the region code of the playback apparatus itself. When the read region code is in accordance, the DVD will be played back. When the read region code is not in accordance, the DVD will not be played back. Due to this region code system, DVDs are distributed only within the area where they are sold, and the distribution does not expand to outside the area represented by the appropriate region code. Accordingly, the aforementioned various sensitive problems are solved altogether.
Two DVDs having a same movie recorded thereon, for example, one distributed in Japan and the other distributed in the U.S.A., could be different in terms of their image qualities and interactive functions. More specifically, some of the DVDs for Japan undergo re-encoding of moving images so that subtitles and Japanese audio can be added. In such a case, the image quality is different from that of the DVDs for the U.S.A. In addition, sometimes an extra bonus called an Easter Egg and the interactive functions associated with the Easter Egg are provided only in the DVDs for the U.S.A. Because there are such differences, many of Japanese business persons who have been living in the U.S.A. for a long time collect and treasure U.S.A. versions of DVDs. When such a business person comes back to Japan and tries to play back the DVDs in his collection on the playback apparatus owned by his family, he finds out that the playback of those DVDs on the playback apparatuses in Japan are prohibited because of the difference in the region codes. Since he is not able to play back the DVDs on playback apparatuses in Japan, the value of his collection, which is personal property, is lowered. The drop in the value gives a bad impression to the user who has purchased the DVDs. It is, however, quit difficult to abolish the restraint with region code system because there are sensitive issues such as the one related to the relationship with the distribution companies in the distribution areas and the like.